BackgroundMembers of the Anopheles gambiae complex are the main transmitters of malaria. Anopheles merus is a member of the complex found along the Kenyan coast because it breeds in saline waters. An entomological study was conducted in Garithe Malindi District, to investigate the physicochemical and environmental factors affecting the distribution of An. merus.MethodsField and laboratory studies were used to investigate the breeding habitats of the subspecies. Mosquito larvae were sampled using standard dipping technique from small pockets of pools, ponds, hoof prints, road drain, wells and mangrove swamps found in Garithe. All 3rd and 4th instars of Anopheles larvae sampled were identified microscopically into species. A representative of Anopheles gambiae complex was then identified to specific sibling species using r-DNA PCR technique.The habitats were characterized based on temperature, conductivity, salinity, dissolved oxygen, total dissolved solids, pH, size, distance to nearest house, canopy coverage, surface debris, presence of algae, emergent plants, turbidity and habitat types.ResultsA total of 159 morphologically identified late stage instar Anopheles gambiae s.l larvae were selected for r-DNA analysis by PCR. Out of these, 60.4% (n = 96) were Anopheles merus, 8.8% (n = 14) were Anopheles arabiensis, 18.2% (n = 29) were Anopheles gambiae s.s and 12.6% (n = 20) were unknown.Using paired t-test (t (121) = −3.331, P = 0.001) a significantly high proportion of An. merus was observed in all habitats compared to An. arabiensis, and An. gambiae s. s.In habitat characterization, Pearson’s correlation analysis test showed different parameters being associated with the occurrence of An. merus larvae in the different habitats sampled. Six out of the 55 correlation coefficients (10.9%) were statistically significant, suggesting non-random association between some pairs of variables. Those that had a significantly high positive correlation with An. merus included temperature, salinity, conductivity, total dissolved solids and algae.ConclusionsDifferent physicochemical parameters and environmental parameters affect the occurrence of An. merus. In this study, higher temperatures accelerate the growth of the larvae and aids in growth of micro-organisms and algae which are food sources for the larvae. Saline waters favour the growth and development of An. merus larvae; they are also able to develop in a range of saline waters. Conductivity, total dissolved solids and canopy coverage are among the important factors influencing the development and abundance of An. merus larvae in their habitats. Habitat type also influences the abundance of An. merus larvae. They mainly prefer to breed in pools and ponds, but not swamps, hoof prints and wells.

BackgroundAnopheles merus, a sibling species of the Anopheles gambiae complex occurs along the East African coast but its biology and role in malaria transmission in this region is poorly understood. We evaluated the blood feeding pattern and the role of this species in malaria transmission in Malindi district, Coastal Kenya.MethodsAdult mosquitoes were collected indoors by CDC light traps and Pyrethrum Spray Catch and outdoors by CDC light traps. Anopheles females were identified to species by morphological characteristics and sibling species of An. gambiae complex distinguished by rDNA polymerase chain reaction (PCR). Screening for host blood meal sources and presence or absence of Plasmodium falciparum circumsporozoite proteins was achieved by Enzyme Linked Immunosorbent Assays (ELISA).ResultsAnopheles merus comprised 77.8% of the 387 Anopheles gambiae s.l adults that were collected. Other sibling species of Anopheles gambiae s.l identified in the study site included An. arabiensis(3.6%), and An. gambiae s.s. (8%). The human blood index for An. merus was 0.12, while the sporozoite rate was 0.3%.ConclusionThese findings suggest that An. merus can play a minor role in malaria transmission along the Kenyan Coast and should be a target for vector control which in turn could be applied in designing and implementing mosquito control programmes targeting marsh-breeding mosquitoes; with the ultimate goal being to reduce the transmission of malaria associated with these vectors.

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SummaryApplication of nitrogenous fertilisers (NPKS 25: 5: 5:5) for yield of tea and to induce tolerance to the red crevice (Brevipalpus phoenicis Geijskes) mite was found to be rates between 150 and 200 Kg N ha‐1 yr‐1 rates above 400 Kg N ha‐1 encouraged the build up of mites on tea. Damage symptoms resulting from mite infestation declined with increase in application of nitrogenous fertilisers.The levels of nitrogen in the leaf tissues increased with soil applied nitrogen and also was related to the mite numbers found on the leaves suggesting a link. The symptoms of the discoloured necrotic leaf base that accompanied mite infestation was significantly (P≤ 0.05) and linearly correlated (r = 0.60) to mite numbers in the control plot. The levels of applied nitrogen were negatively correlated to % leaf necrosis suggesting a tolerance leading to reduction in necrotic symptoms with fertiliser applications.

There were significant differences in the level of susceptibility among the 12 varieties which were screened for resistance to A. lycopersicL Pronounced tolerance to leaf damage was recorded on varieties Early Stone Improved and Beauty. Oxheart and Bonny Best both of which had comparatively lower mite densities were highly susceptible. Flower bud formation was not significantly affected by the mite damage. However, the number of dead flowers and flower buds on infested plants was significantly more than on protected ones.Russetting of young fruits due to mite damage differed significantly among the varieties tested, and was positively correlated with moisture content of young fruits. The least and most affected varieties were Beauty and Red Cioud respectively. The percentage yield loss was highest on Hybrid Beefmaster and Oxheart and lowest on Roma and Money Maker.Resume-Des differences signiflcatives existent quant au degr£ de sensibility des varietes de tomate testers pour la resistance a A. lycopersicL Une tolerance remarquable aux degats foiiaires a iti observed sur les vartetes "Early Stone Improved", et "Beauty". "Oxheart" et "Bonny" sur lesquelles on observe des densites faibles de mites sont aussi sensibles. La formation de boutons floraux n'est pas affected de facon significative par les degats dus aux mites. Cependant, le nombre de fleurs et de boutons floraux desseche's sur les plantes infestSes est signiflcativement plus important que sur celles protegees. Le bruinissement des jeunes fruits du aux degfits des mites est significativement different entre les varie'te's testees; et il existe une correlation positive avec le taux d'humidite des jeunes fruits. Les varietes les plus et moins affectees sont "Beauty" et "Red Cloud" respectivement. Le pourcentage de.perte en rendement est le plus eleve" sur Phybride "Beef Master" et "Oxheart" alors qu'il est le pips bas sur "Roma" et "Money Maker".

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Agroecosystems in the tropics include growing two or more crops in diverse polycultural patterns. In Kenya, cowpea Vigna unguiculata (Walp.) is grown in combination with cereals such as maize and sorghum, perennial legumes such as pigeon peas and root crops such as cassava and sweet potatoes. In the present investigations, field experiments were conducted to study the incidence and damage caused by Clavigralla tomentoscollis Germ, and C. shadabi, after flowering, on cowpea intercropped with maize. It was evident from the present studies that C. tomentoscollis and C. shadabi were more prevalent on cowpea during the first season rather than during the second season. Both species had a preference for feeding on cowpea intercropped with maize than when it was grown in pure stands. Consequently more pod damage was recorded on cowpea planted with maize. It was therefore concluded that this agricultural system, which is commonly practised by smallscale farmers in Kenya, is undesirable from the point of view of bug damage.